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Glossary of IT Infrastructure Library Terms (ITIL®)

Glossary of Terms for the IT Infrastructure Library
Mar 4, 2004

ITSM Watch Staff




Redundant Array of Inexpensive Disks - a mechanism for providing data resilience for computer systems using mirrored arrays of magnetic disks.


Different levels of RAID can be applied to provide for greater resilience.


reference data
Information that supports the plans and action lists, such as names and addresses or inventories, which is indexed within the plan.


A collection of new and/or changed CIs which are tested and introduced into the live environment together.


remote fixes
Incidents or problems resolved without a member of the support staff visiting the physical location of the problems.


Note: Fixing incidents or problems remotely minimizes the delay before the service is back to normal and is therefore usually cost-effective.


Request For Change (RFC)
Form, or screen, used to record details of a request for a change to any CI within an infrastructure or to procedures and items associated with the infrastructure.


Action which will resolve an incident. This may be a Workaround.


resource cost
The amount of machine resource that a given task consumes. This resource is usually expressed in seconds for the CPU or the number of I/Os for a disk or tape device.


resource profile
The total resource costs that are consumed by an individual on-line transaction, batch job or program. It is usually expressed in terms of CPU seconds, number of I/Os and memory usage.


resource unit costs
Resource units may be calculated on a standard cost basis to identify the expected (standard) cost for using a particular resource. Because computer resources come in many shapes and forms, units have to be established by logical groupings.


Examples are:

  • CPU time or instructions
  • disk I/Os
  • print lines
  • communication transactions

The IT services section needs to provide the customers with the required services. The resources are typically computer and related equipment, software, facilities or organizational (people).


Return On Investment
The ratio of the cost of implementing a project, product or service and the savings as a result of completing the activity in terms of either internal savings, increased external revenue or a combination of the two. For instance, in simplistic terms if the internal cost of ICT cabling of office moves is $100,000 per annum and a structured cabling system can be installed for $300,000, then an ROI will be achieved after approximately three years.


return to normal phase
The phase within a business recovery plan which reestablishes normal operations.


A measure of the exposure to which an organization may be subjected. This is a combination of the likelihood of a business disruption occurring and the possible loss that may result from such business disruption.


risk analysis
The identification and assessment of the level (measure) of the risks calculated from the assessed values of assets and the assessed levels of threats to, and vulnerabilities of, those assets.


Risk Management
The identification, selection and adoption of countermeasures justified by the identified risks to assets in terms of their potential impact upon services if failure occurs, and the reduction of those risks to an acceptable level.


Risk reduction measure
Measures taken to reduce the likelihood or consequences of a business disruption occurring (as opposed to planning to recover after a disruption).


A set of responsibilities, activities and authorizations.


roll in, roll out (RIRO)
Used on some systems to describe swapping.


Rotational Position Sensing
A facility which is employed on most mainframes and some minicomputers. When a seek has been initiated the system can free the path from a disk drive to a controller for use by another disk drive, while it is waiting for the required data to come under the read/write heads (latency). This facility usually improves the overall performance of the I/O subsystem.